Specialized knives are used in industrial wood processing machines such as chippers, canters, and planers. A plurality of such knives are replaceably mounted to a rotating cutting head. The wood is fed toward the head so that it will come into interference with the knives, whereupon the rotation of the knives causes the knives to cut chips, wafers, strands, or shavings from the wood. This can be either or both for the purpose of shaping the wood to a desired configuration, or for producing the cuttings as commercially desired end products.
The knives have cutting edges that should remain sharp for as long as practical, and the knives must be strong enough to withstand the tremendous forces applied to them as they impact the wood at high rates of speed. The earliest such knives were large, monolithic plates of metal bolted directly to the cutting head, one side of which were cut to form an acute angle for use as a cutting edge. An example is shown in FIG. 1. Such knives are still in use today, but there is a problem. The cutting edge must be repeatedly renewed (by grinding), the knives must be removed from the cutting apparatus to perform this maintenance, and the weight of the knives makes them difficult to handle.
To address this problem, the art evolved smaller, lighter knives clamped in supporting structures to form “knife assemblies.” Typically, a knife assembly has a knife clamped between upper and lower clamping members, with the lower clamping member being bolted to the cutting head rather than the knife itself. An example is shown in FIG. 2 with reference to a direction of rotation “R,” where a knife assembly 3 is shown which includes the knife of FIG. 1 (referenced as 2) clamped between upper and lower clamping members 3a and 3b, respectively.
Also shown in FIG. 2 is an optional structure 3c known as a “counterknife” or “wear insert.” Both the knife 2 and the counterknife or wear insert 3c are relatively small parts that are the focus of the wear imposed upon the knife assembly, and both of these parts can be relatively easily handled for repair or replacement due to their significantly reduced mass as compared to the remainder of the knife assembly.
By use of the knife assembly, a knife could be made small enough that, in view of its reduced material cost, it could be cost-effective to dispose of the knife rather than perform the maintenance required to keep its cutting edge fresh after it has become worn.
Another important development in the art was the double-sided knife, an example being shown in FIG. 3. As the name implies, the double-sided knife has two cutting edges on opposite sides thereof. Thus, when the first cutting edge wears, the knife can be removed from the knife assembly, turned end-for-end, and reinstalled in the knife assembly to expose a fresh new cutting edge, doubling the cutting life of the knife.
Despite these important developments in the art, large, unsupported and therefore heavy knives such as that shown in FIG. 2 continue to be used in existing, legacy wood processing machines, and there remain a number of operators of industrial wood processing machines that are well adapted for maintaining knives, and prefer to service a knife to extend its life rather than replace it with a disposable version. But further improvements in cost efficiency would be desirable, and continued progress in making the strategy of disposing of worn knives rather than repairing them cost effective would also be desirable.